1. Field of the Invention
This invention relates to thermal degradation of hair, and, more particularly, to a method of protecting hair against such degradation when heat treated with thermal styling appliances to impart desirable styling characteristics to the hair.
2. Description of the Prior Art
Several commercial products are available to protect hair from heat styling appliances. These products often contain a wide range of actives including hydrolyzed proteins, enzyme cofactors, fatty acids, saccharides, surfactants, and various polymers. Hydrolyzed wheat protein, wheat oligosaccharides, wheat amino acids, and panthenol, when formulated together, are believed to increase the strength and moisture retention of hair fibers when used in conjunction with a thermal styling appliance. Additionally, the thermal protection properties of PVP and panthenol have been investigated outside of a formulation. Several patents specifically identify a compound or formulation as a thermal protector against hair dryers or hot irons. For hair dryer protection, the following systems were prescribed: high molecular weight silicone and fatty acid alkanol amides; mono-N-acyl basic amino acid lower alkyl ester salt and/or cationic surfactant, liquid oil, and heme iron compound; quaternary ammonium salts, one or a mixture of crude extract from the rind of fruits, and a water-soluble polymers having a quaternary nitrogens; and a conditioner containing stearyltrimethyl-ammonium chloride and polyethylene-polypropylene glycol butyl ether as its actives. There are also patents that strictly relate to protecting hair from hot irons. One formulation includes a two-phase system and a surfactant. The oil phase consists of one or a mixture of ester oils, triglycerides, higher alcohols, animal oils, plant oils, and silicone oils while the aqueous phase contains glycerol, propylene glycol, and polyethylene glycol. The surfactant may be nonionic, cationic, or anionic. Another composition, consisting of polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oils, fatty acids (from animal or vegetable sources), and a nonionic surfactant, has also been suggested to protect hair from hot irons.
Several compounds have been used as thermal setting agents, in which the active is applied to hair prior to or during thermal treatment. Specifically, the application of a thermoplastic polyester fixative resin used in conjunction with a thermal styling appliance has been described in the patent literature. Similar to hair fibers, cotton fibers may experience similar interactions with compounds when subjected to high temperatures. The cross-linking of cellulose with polycarboxylic acids has received a significant amount of attention within the textile industry as an alternative method for permanent pressing finished cotton fabrics.
The thermal yellowing of wool, and its prevention, represents another important problem within the textile industry. Although the mechanism of wool thermal yellowing and its prevention are not fully understood, several compounds have been identified as inhibitors of yellowing. Most significantly, maleic anhydride was found to retard wool thermal yellowing to a significant degree. A similar effect was observed when wool was immersed in dilute H.sub.2 SO.sub.4 prior to thermal exposure. Overall, evidence indicates that the yellowing of wool is pH sensitive, with the degree of yellowing increasing with increasing pH.
Accordingly, it is an object of this invention to provide a method of protecting hair or wool against thermal degradation when heat treated at elevated temperatures.
A feature of the invention is the application of a composition of methyl vinyl ether-maleic acid copolymer, to protect hair or wool against thermal degradation when heat treated at 100-180.degree. C.